Plants grown is a standard hydroponic system go through a period of vegetative growth that lasts 4 weeks, followed by a period of flowering growth that lasts 8 – 10 weeks. Total grow time from clone to harvest is approximately 12 – 14 weeks.
There are 14 essential minerals in fertilizers that plants require for life. Macro nutrients are used by plants in the highest amounts. Micro nutrients are used in smaller amounts but are still required for life.
Water by itself is not enough to feed your plants. Water contains some native minerals but not enough, or all the required minerals. Fertilizer supplements containing all 14 essential minerals must be added to your water to create a feeding solution.
Hydroponic plants require a very precise application of fertilizer. Dosages vary from week to week, supplying plants ideal nutrition for their stage of growth, while avoiding excesses that cause toxifying salt buildups in the grow media.
In a hydroponic system, there are specific fertilizers designed to provide all the essential minerals required for plant growth – except sometimes calcium and magnesium which may require a separate product. These fertilizers are typically labeled for specific weeks of plant growth and contain precise proportions of minerals tailored to meet the exact requirements of each growth stage. For instance, a fertilizer labeled for Weeks 1 & 4 may contain more phosphorus during the first week of growth to support root strike and during the fourth week to initiate budding. The goal of using these hydroponic fertilizers is to provide the exact nutrients plants need for the indicated weeks of growth to ensure healthy and optimal plant development.
Calcium and Magnesium is a separate product from all the other minerals for reasons explained here.
In a hydroponic fertilizer system, it is recommended to package calcium and magnesium as a separate product from all the other essential minerals. This is because calcium should not be dissolved with water at the same time as phosphorus and sulfur, as they can bind together and form insoluble clumps. To avoid this issue, it is best to dissolve calcium and magnesium fertilizer with water separately and then mix it with the other fertilizers.
The dosage of calcium and magnesium should be adjusted according to the starting state of the irrigation water. If using tap water, it is important to consider that there is already calcium and magnesium present in the water, so less fertilizer is needed to be added to it. However, if the water contains little or no calcium and magnesium, such as rain water or R/O water, then more calcium and magnesium should be added to it. The starting state of water before adding any other minerals should be approximately 0.3 EC (300 TDS) of mostly calcium and magnesium.
The average volume of calcium and magnesium in tap water is 0.15 EC (150 TDS), but this can vary significantly from region to region. To determine the amount of calcium and magnesium in your water, you can check your municipality’s website, use commercially available testing strips, or use an EC meter to measure the water’s mineral content.
In hydroponic fertilizer systems, there may be different kits available for different types of water. For instance, there could be one kit for R/O water, which contains a full supplement of calcium and magnesium, and another kit for tap water, which contains half the calcium and magnesium as the R/O water kit because tap water already contains native calcium and magnesium and doesn’t need as much extra added by fertilizer.
*R/O water is water that has had all its mineral content removed. It is sometimes called inert water.
Fertilizers designed for hydroponics require a precise application of fertilizers. The volume of minerals in a feeding solution must be carefully measured and then regularly monitored throughout the grow cycle to maintain ranges that are safe for plants.
The volume of minerals dissolved in water is measured using an EC metre. EC stands for Electric Conductivity. EC metres work by measuring resistance to an electrical charge between two filaments while submerged in a feeding solution. Dissolved solids affect resistance allowing the EC metre to approximate the volume of dissolved solids in water.
Environmental factors, such as volume of light, as well as differences with plant strains, can cause plants to consume more of less fertilizer. Regular monitoring of your irrigation reservoir using a EC metre allows you to fine tune your fertilizer dosage. EC metres are also helpful when mixing fertilizer to verify safe ranges.
Some EC metres output their measurement as TDS or PPM instead of EC. TDS stands for Total Dissolved Solids and PPM stands for Parts Per Million. TDS or PPM are different standards of measurement, similar to inches compared to centimetres.
A conversion from EC to the other measurement standards is simple:
1 EC = 500 TDS 1 EC = 700 PPM or 500 PPM*
*PPM is not a consistent measurement standard because sometimes it is 500 EC and sometimes its 700 EC. Use EC or TDS for your measurement standard to avoid accidental calculation errors.
The pH scale is the measurement of how acidic or basic water is, ranging from 0 to 14. 7 is neutral—neither acidic nor basic. A number lower than 7 is acidic. A number higher than 7 is basic.
The pH of water changes when acidic or basic substances are added to it. For example, adding minerals changes the pH of water because minerals have acidic and basic properties. Some substances are more acidic or basic than others and will have a greater influence on the pH of your water than others.
Accurate measurement of pH is important because the pH of water affects a plant’s ability to absorb minerals efficiently. When pH is out of range in the irrigation water a plant can even become blocked from absorbing nutrients that they need to survive.
pH also has an effect on the solubility of minerals. Minerals are soluble when water has a pH of 5.6-6.4. If pH drifts out of this range, minerals can precipitate out of solution. For example, calcium, iron and phosphate start to leave solution when pH rises above 6.5.
The pH of a feeding solution for cannabis plants should be kept between 5.8-6.3. This range optimizes mineral solubility and uptake.
The pH of water is measured using an electronic pH meter. pH meters must be calibrated before use using calibration solutions.
Growers adjust the pH of their solutions with commercially available pH Up and pH Down solutions. pH Up is a concentrated base that raises pH. pH Down is a concentrated acid that lowers pH.
pH up and down solutions are very concentrated and are best administered to water with a syringe or dropper.
pH needs to be monitored regularly throughout the entire growing process and adjusted to keep it within recommended range.
Rain, tap or well water always comes pre-loaded with some native substances before fertilizer gets added to it. When water has more substances than average it’s called hard water. When water has less substances than average it’s called soft water.
The predominant minerals found natively in tap water are calcium and magnesium.
A measurement of your water taken before nutrients are added will determine its hardness:
Very Soft Water – rain water and R/O water. 0-70 TDS 0 – 0.14 EC
Soft Water – average tap water. 70-140 TDS 0.14 – 0.28 EC
Slightly Hard Water – average tap water. 140-210 TDS 0.28 – 0.42 EC
Moderately Hard Water 210-320 TDS 0.42 – 0.64 EC
Hard Water – Very difficult to work with. 320-530 TDS 0.64 – 1.06 EC
R/O or rain water is Very Soft, close to 0 EC (0 TDS). Tap water is often around 0.1 EC (150 TDS), but this depends on municipality. Use Cal-Mag to raise the mineral content of your water. An EC metre can tell you when you’ve added enough Cal-Mag to your irrigation water to reach a target dosage of 0.3 EC (300 TDS).
Excessively hard water is very difficult to work with because adding fertilizers to water that is already crowded with minerals creates a toxic solution. To fix hard water use a reverse osmosis process to take minerals out, then put fertilizer in.
After treating water with a reverse osmosis machine, add calcium and magnesium back to it at a 2:1 ratio, raising its mineral content to 0.3 EC (300 TDS).
When nutrients are added to water the resulting mixture is called a feeding solution.
There are maximum limits for how many minerals should be in a feeding solution for each stage of plant growth. When nutrients are present at healthy levels, plants are able to uptake and use them effectively. When there’s an excess of minerals, a build up accumulates in the growing media which can cause several serious problems:
Mineral buildup can cause plants to stop taking up water.
Minerals trapped in the growing media bind with minerals in the feeding solution, blocking plants from absorbing the bound minerals. This leads to a nutrient deficiency of the minerals that are bound.
Mineral buildup in the grow media causes pH to swing in the roots zone. Irregular pH causes minerals to precipitate out of solution and prevents plants from absorbing minerals.
Mineral buildups occur when plants are fed more minerals than they can absorb and they should be avoided.
The total amount of minerals that should be in a feeding solution depends on plant’s stage of growth. Young seedlings and clones use fewer minerals. As plants get older and larger they use more minerals, until they reach late bloom when they start to consume less.
The list below details the total approximate recommended mineral concentration after all nutrients and additives have been added to water for all the growth stages of cannabis. Maintaining a feeding solution within these ranges helps prevent over fertilization problems.
Water sourced from the tap can contain too much chlorine. Chlorine gets added at the municipal reservoir to kill microorganisms and bacteria to make drinking water more safe for humans. For plants, high levels of chlorine are harmful to their root zone and therefore should be removed. Before adding any fertilizers, remove chlorine from your tap water using a chlorine filter. Vitamin C (ascorbic acid) tablets will also get rid of chlorine.
Fertilized irrigation water can attract fungi infections that consume nutrients. This is bad because fungi destroys fertilizer so plants can’t use it. Prevent fungi colonies from developing by adding sodium benzonate to the irrigation water at a concentration of .13 gram / 100 litres.
Powdered fertilizers must be dissolved with water before use. Dissolve powders thoroughly in a small volume of water, then pour the resulting solution into a larger volume of water. Heating water helps powders dissolve better. Calcium and magnesium powdered fertilizer needs to dissolved with water independently of other fertilizers because it can cause clumping when mixed at same time with phosphorus and sulphur. Always use a mask when working with fertilizers to avoid inhalation.
Plant stimulants aid in how plants process minerals. They help plants access and take up water and minerals more effectively. Bio-stimulants make plants more productive and stress resistant, improving growth results beyond what can be achieved with mineral fertilizers alone.
Examples of some different types of plant stimulants:
Humic Acid and Amino Acid are chelators. Chelators help plants take up minerals better.
Kelp extract contains growth hormones that are beneficial for stimulating plant growth processes.
Yucca is a speading agent that helps feeding solution spread out better on the leaf surface and in grow media, improving nutrient absorption by plants.
Bio-stimulants are not fertilizer. They enhance the effectiveness of fertilizer. They are not required for plant life but will help you optimize your garden for best results.
Roots are not the only way plants can absorb nutrients. Plants are also able to absorb nutrients through their leaves. Foliar sprays are feeding solutions that are sprayed on a plants leaves.
Foliar sprays can help clones root faster. Cuttings taken from a mother plant to make clones have no roots and no other way to absorb water & nutrients except through their foliage. During their rooting period, clones are kept on life support in a humidity dome where they survive only by absorbing water & nutrients through their foliage from the air. Support vulnerable clones with foliar feeding directly on their leaves. Apply a foliar spray containing Kelp Extract and Humic Acid to clones because it will speed up their root development and boost their survival rate.
Foliar sprays are also very effective for emergency first-aid correction of nutrient deficiencies. Plants can absorb nutrients sprayed directly on their leaves more immediately than absorption through their roots. If your plants have a nutrient deficiency, apply a foliar spray in addition to correcting their feeding solution because foliar absorption offers the advantage of speed. A faster delivery of deficient minerals reduces stress and damage and can in more extreme cases make the difference between life and death for your plants.
A foliar spray is improved with the addition of yucca extract. Yucca is a water spreading agent that makes water spread out and cover a leaf’s surface rather than beading up, allowing nutrients to be more thoroughly distributed and absorbed. Add some yucca to your Foliar sprays to make them work better.
Foliar sprays should not be applied under strong lighting because water can act as a lens that can burn foliage. Apply foliar sprays only when lights are off.
Not all products should be used as a foliar spray, and some products should only be applied as a foliar spray during the vegetative growth phase. Before using a product in a foliar spray check if it is indicated for foliar use and which stages of growth it can be used.